1. Field of the Invention
This invention relates to a process for the preparation of a novel diphenylamine in which each phenyl group is substituted. Diphenylamines available according to the present invention are useful as antioxidants for mineral oils, synthetic oils and the like and also as resin additives.
2. Description of the Related Art
As a process for the preparation of a diphenylamine containing one or more substituents on each phenyl group, it has already been known to prepare dinonyldiphenylamine by subjecting nonene and diphenylamine to Friedel-Crafts alkylation in the presence of a metal halide such as aluminum chloride or zinc chloride or an acid catalyst such as sulfuric acid, phosphoric acid or acid clay (Japanese Patent Laid-Open No. 188555/1990).
This process, however, is accompanied with the drawback that it is difficult to add a sufficient amount of nonene to diphenylamine. Thus, the resultant dinonyldiphenylamine contains the mono-substituted derivative and is low in purity.